During the reign of Henry II (1154 to 1189), to regain for the crown the powers usurped by Thomas Becket, Chancellor of England, 12 “good and lawful men” in each village were assembled to reveal the names of those suspected of crimes. It was during this same period that juries were divided into two types, civil and criminal, with the development of each influencing the other.
The Court had long taken the position that a jury in a criminal case must have 12 members.Twentieth century "law office history" seems to hold that the size of the jury is to provide a "cross-section" of the public In 1898, the Court said, "a jury comprised of 12 persons, neither more or less" was a constitutional requirement. In 1970, in Williams v Florida, they Court reconsidered its earlier statements on jury size in a case that affirmed the conviction of a robber convicted by a six-member Florida jury. The Court noted that the Sixth Amendment says nothing at all about jury size, even though 12 person-juries had been traditionally used in America. The expectation that a jury consists of 12 members dated back to the 1300s, but the Court found that to be a "historical accident." Concluding that a six-person jury could fulfill the framers' expectations concerning a jury's functions just as well as a 12-person jury, the Court rejected its prior words on the subject and held that six-person juries satisfy the requirements of the Sixth and Fourteenth Amendments. Justice Harlan harshly criticized the majority's reasoning, asking where and how the Court might draw the line on jury size. Would a three-person jury be okay, he wondered??